Many building codes are now requiring or will soon require hurricane shutters on all new homes built in coastal areas. Similar requirements for buildings other than homes are anticipated as well. The South Florida Building Code, 1994 Edition, requires that storm shutters shall be designed and constructed to insure a minimum of a one inch separation at maximum deflection with components and frames of components they are to protect unless the components and frame are designed to receive the load of storm shutters.
The determination of actual wind loading on building surfaces is complex and varies with wind direction, time, height above ground, building shape, terrain, surrounding structures, and other factors. The American Society For Testing And Materials (ASTM) has promulgated a Standard Test Method For Structural Performance of Exterior Windows, Curtain Walls, And Doors By Uniform Static Air Pressure Difference and its designation is E330-97 and was published April 1998. The test method requires that the person specifying the test translate anticipated wind velocities and durations into uniform static air pressure differences and durations. Durations are considered because most materials have strength or deflection characteristics which are time dependent. Testing under this method is performed in a test chamber which measures the pressure difference across the test specimen.
Similarly, ASTM has declared a Standard Test Method For Water Penetration Of Exterior Windows, Curtain Walls, And Doors By Uniform Static Air Pressure Difference which includes a water spraying apparatus within the test chamber. See, ASTM designation E331-96. Leakage rate testing can be done under the ASTM Standard Test Method For Determining The Rate Of Air Leakage Through Exterior Windows, Curtain Walls And Doors Under Specified Pressure Differences Across The Specimen. See, ASTM designation E283-91.
When a building envelope is breached devastating pressure differentials cause large amounts of damage. Kinetic energy due to the velocity of the fluid is proportional to the square of the velocity. Energy from the wind, therefore, pressurizes the interior of a home or other structure which in combination with the profile of the roof makes the roof, in effect, act like an airplane wing causing it to blow off the remaining structure. Windload and impact resistance requirements depend on the particular community promulgating the requirements.
The American Society of Civil Engineers' Standard 7 is being increasingly used by public regulators in formulating requirements. In some areas of high probability for high wind occurrences, such as hurricanes, existing homes are required to upgrade windows and doors or add shutters and other protective devices to building openings to protect them.
Conventional storm window protection as shown in U.S. Pat. No. 4,065,900 to Eggert, U.S. Pat. No. 4,069,641 to De Zutter and U.S. Pat. No. 4,478,268 to Palmer are methods of attaching outer coverings to window or door openings. U.S. Pat. No. 4,065,900 to Eggert discloses an apparatus for framing and fastening a secondary glazing pane which utilizes a hinge. U.S. Pat. No. 4,069,641 to De Zutter discloses a storm window frame which utilizes double-faced tape to mount the storm window frame and, hence, the storm window. U.S. Pat. No. 4,478,268 to Palmer discloses a hard flexible curtain door, a tensioned storage or wind-up drum, and channels in which the door resides. The door moves out of the channels under impact and is wound up to open for vehicle passage.
U.S. Pat. No. 4,126,174 to Moriarty, et al. discloses a tensioned flexible sheet storage roller, a guide roller and side seal guides. These coverings are normally clear flexible materials that must be installed and removed as needed or can be rolled and stored in a storage area above the window. These materials can be tinted to provide a reduction in sunlight transmission, but tinting would also reduce vision at night. These storm window coverings offer good thermal insulation, but offer minimal protection from high wind velocity pressures and wind borne debris. Further, these coverings are usually made of flexible polyvinyl chloride and will functionally deteriorate with time and must be replaced. The coverings that are of rolling construction must have adequate clearance between the guide rails and the sheet to prevent jamming of the sheet in the guide rails during opening and closing.
U.S. Pat. No. 4,294,302 to Ricke, Sr. discloses a security shutter and awning device for covering windows and doors. The device includes slats made from aluminum or other extrudable material of sufficient strength to protect against storms and/or vandalism. The shutter of Ricke, Sr. may be slidably mounted and pivoted so as to act as an awning.
U.S. Pat. No. 4,601,320 to Taylor discloses a pressure differential compensating flexible curtain with side edge sections which are sealingly engaged with channels. The first upper end of the curtain is attached to a curtain winding mechanism which includes a spring barrel. Taylor discloses an elastomeric curtain having plastic supports with rubber covers banded thereto. Alternatively the plastic supports may be high molecular weight plastic strips. The purpose behind the design of the supports is to minimize the friction of these supports enabling operation of the door/curtain with a high differential pressure across it.
U.S. Pat. No. 4,723,588 to Ruppel discloses a roller shutter slat which interlocks with the adjacent roller sheet slat. U.S. Pat. No. 5,657,805 to Magro discloses a wind-resistant overhead closure with windlocks on the lateral edge portions of the intermediate and bottommost slats of the closure. First means to limit the lateral movement of the lateral edge of the intermediate potions and second means to limit the lateral movement of the endmost door portion are disclosed. Intermediate slats and endmost slats are provided. The '805 patent indicates in col. 2, lines 12 et seq. that it conforms with the South Florida Building Code, 1994 Edition, previously referred to hereinabove. Further, the '805 patent states that its teachings are applicable to both doors and windows.
Windlocks can be added at the end of slats which will improve the resistance of multileaf shutters or doors to wind velocity pressures by transmitting the stresses on the continuous hinge area to the ends of the slat, to the guide system and finally to the jambs or building structure. In order for the windlocks to engage the guide track the slat must deflect a considerable amount. Normally clearance is allowed between the guide track and the windlock to keep the door from jamming during operation and the more clearance allowed the more deflection of the slats before the windlocks contact the guide track. Typically, these windlocks are larger in cross section than the slat profile and when the shutter or door deflects from high wind velocity pressures, the windlocks are designed to engage the same space in which the slats are guided. When storing a rolling multileaf shutter or door equipped with windlocks, additional room is needed because the depth of the windlock is larger than the slat profile, the diameter of the storage area increases dramatically. In these designs, clearance between the windlock and the track must be allowed to prevent the windlocks from jamming and care must be taken when operating shutters or doors in a wind because the windlocks will sometimes jam as the product deflects.
U.S. Pat. No. 5,445,902 to Lichy discloses a damage minimizing closure door somewhat similar to U.S. Pat. No. 4,478,268 to Palmer. The Lichy '209 patent discloses a flexible curtain and a guide for receiving and guiding the side edges of the flexible door during vertical movement. A counterbalancing power spring is associated with the door to assist in raising and lowering the curtain. Side edges of the curtain separate from the guide assembly upon being impacted by an externally applied force such as a vehicle.
U.S. Pat. No. 5,482,104 to Lichy discloses in FIG. 17 thereof, a flexible curtain and double windlocks which breakaway from the channel upon the application of excessive force to the curtain. See, col. 7, lines 33 et seq. U.S. Pat. No. 5,131,450 to Lichy discloses in FIG. 6 thereof a double edged guide and a curtain edge with two loose portions sewn to the transverse curtain. See, col. 6, lines 21, et seq. U.S. Pat. No. 5,232,408 to Brown discloses a flexible tape drive system wherein the tape is relatively rigid and it is driven by a toothed cog to provide both push and pull capabilities. U.S. Pat. No. 5,048,739 to Unoma, et al. illustrates a conical toothed drive paper feeder.
Conventional storm curtains without windlocks to engage into guides will pull out of the guides. This is especially true of wider curtains where they might be partially lowered for shading purposes without attaching storm bars required for storm protection. If, while lowering, or subsequent to lowering, wind forces exist that are significant but in no way threatening, the storm curtains typically escape from the guides due to excessive deflection of the slats. When this occurs, the slats become damaged as well as the facade surrounding the guide area becomes damaged as the ends of the slats typically rake the surrounding area in the process of escaping. The majority of applications for conventional storm curtains do not use windlocks. Rather than using windlocks, the problem of excessive curtain deflection which causes the curtain to escape from the guides is addressed with the use of storm bars. Storm bars, however, have disadvantages.
Storm bars create a passive system i.e. in the event of a severe storm they need to be taken out of storage and attached in predetermined locations across the span of the curtain. A wide curtain may require as many as three sets of storm bars. Sets consist of two bars in close proximity to each other in such a way as the curtain passes between the two bars. This addresses deflection that occurs in both positive and negative directions. Positive deflection is in the direction of the building and negative deflection is away from the building. At each storm bar location, brackets must first be attached to the floor, soffit and sills. Depending on the surrounding construction materials, secure locations are often difficult to find. After the brackets are attached to the building, the next step is to attach the storm bars to the brackets. Care must be taken to number and code the brackets to the matching storm bar, otherwise the pre-drilled holes for the bolts will not line up with the holes in the storm bars. Also, care must be taken to match and code the storm bars to their various locations since even a slight variation in the bar length causes the holes in the storm bar to misalign with the pre-drilled holes in the building facade. Also, these pre-drilled holes in the facade are permanent and cause problems aesthetically when the storm bar brackets are removed. Given the problems associated with escaping storm curtains, the building owner faces a dilemma when moderate storms are predicted such as severe summertime thunder storms. The daunting task of attaching the storm bars cannot be justified for every storm. Because the risk of damaging the storm curtains without attaching the storm bars is so great, the curtains are not utilized in moderate storms. Therefore, the building owner has a protection system that is either "on or off," "on" meaning storm bars and curtains and "off" meaning nothing at all.
Conventional storm curtains do not have windlocks to prevent the slats from escaping the guides because windlocks have a larger cross section than that of the slat and using windlocks increases storage coil diameter which is a major limiting factor. With windlocks of the related art, storm curtains have a tendency to bind in the guides/tracks when being lowered because of the deflection of the curtain in moderate wind conditions. Enough friction is created, windlock to the inside edge of the guide, to cause the curtain to become obstructed and create unwanted accumulation of slats in the coil storage area. Additionally, adding windlocks to the ends of slats is very labor intensive and creates many more parts to drill and attach.
The instant invention addresses these three issues. The first issue with conventional storm curtains, that being an increase in coil storage requirement, is addressed by utilizing an interrupt formed on the ends of the tension rods of the instant invention which does not increase the requirement for coil storage when the curtain is stored.
The second issue regarding binding of the curtain is addressed by the instant invention since the tracks are mounted at a divergent angle with respect to each other and contact with the interrupts in the rod and the "J-shaped" channel does not occur until the guide is in a fully closed position minimizing friction. Further, in the instant invention, unwanted accumulation in the coil storage area does not occur and the drive system is able to generate downward closing forces that overcome minimal friction that may occur between the interrupt and the "J-shaped" channel.
Finally, regarding the issue of windlocks being labor intensive, the interrupts formed near the ends of the rods in the instant invention are made with a single stroke of a press after the rods are inserted into the curtain and, as such, do not make the windlock system labor intensive.